1. Field of the Invention
The present invention relates to an air conditioner having two compressors.
2. Background Art
Conventionally, in an air conditioner having two compressors, each compressor has a phase advance capacitor and a starting capacitor, which increases the starting torque to start the compressor. After a compressor is started, the starting capacitor is separated from the circuit by a relay which detects the auxiliary coil current drawn by the compressor motor. One such conventional air conditioner is disclosed in Japanese Patent Unexamined Publication No. H10-019397.
The conventional technique, however, has the following problems.
FIG. 4 is an electrical circuit diagram of a conventional air conditioner. Of two compressors, first compressor 1 includes main coil 2 and auxiliary coil 3. Auxiliary coil 3 is connected to phase advance capacitor 4, and phase advance capacitor 4 is connected in parallel with starting capacitor 5 via cutout relay 6. The contact of cutout relay 6 is closed when cutout relay coil 7 is not supplied with current and is open when cutout relay coil 7 is supplied with current. Cutout relay coil 7 is connected in parallel with auxiliary coil 3.
Before first compressor 1 is started, auxiliary coil 3 is not supplied with current and hence cutout relay coil 7 is not supplied with current either. Therefore, the contact of cutout relay 6 is in a closed position. Phase advance capacitor 4 and starting capacitor 5 are thus connected in parallel with each other so as to increase the starting torque of first compressor 1.
As soon as first compressor 1 is started, auxiliary coil 3 and cutout relay coil 7 are supplied with current at the same time. As a result, the contact of cutout relay 6 is opened, thereby separating starting capacitor 5 from the circuit. The other compressor, second compressor 8, has the same structure as first compressor 1. First compressor 1 and second compressor 8 are connected in parallel with each other.
As described above, starting capacitor 5 is provided in the respective compressors so as to contribute to an increase in the starting torque. Conventionally, however, each compressor is required to have its own starting capacitor 5 although starting capacitor 5 is not used except when the compressor is started. The provision of starting capacitor 5 makes it difficult to make the system inexpensive.